I've seen people report this bug before, but for 1.11.2, it seems like it's back now.
When I set fullscreen mode to false, the game disappears for a few seconds then reappears in windowed form in the top right of my screen, disappears again, the screen goes black, then reappears in the middle of my screen. If I set fullscreen to true, it crashes.
Incomplete without a crash report from (minecraft/crash-reports/crash-<DATE>-client.txt). Please attach it to this ticket so that we can diagnose your issue.